CN114200367A - Saturated band magnetic resonance imaging scanning method and device and magnetic resonance imaging system - Google Patents
Saturated band magnetic resonance imaging scanning method and device and magnetic resonance imaging system Download PDFInfo
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Abstract
The embodiment of the invention discloses a saturated zone magnetic resonance imaging scanning method, a saturated zone magnetic resonance imaging scanning device and a magnetic resonance imaging system. The method comprises the following steps: acquiring the position of a saturation band of saturation band magnetic resonance imaging; acquiring the position of an imaged region of interest; taking a direction pointing from the saturation zone to the region of interest as a first direction; determining the gradient direction of the selected layer; and when the gradient direction of the selected layer is opposite to the first direction, the gradient sign of the applied selected layer gradient is negative and the corresponding magnetic field strength is gradually reduced. According to the embodiment of the invention, the chemical shift direction caused by the gradient of the selected layer in the saturation zone is always far away from the region of interest, so that the false excitation of the region of interest by the saturation pulse can be avoided without changing the width of the saturation zone.
Description
Technical Field
The invention relates to the technical field of Magnetic Resonance Imaging (MRI), in particular to a saturation band MRI scanning method, a saturation band MRI scanning device and an MRI system.
Background
MRI generates an MR (Magnetic Resonance) phenomenon by applying an RF (Radio Frequency) pulse of a certain specific Frequency to a human body in a static Magnetic field to excite hydrogen protons in the human body, and after the pulse is stopped, the protons generate an MR signal in a relaxation process, and an MR image is generated through processing processes such as reception of the MR signal, spatial encoding, and image reconstruction.
In the imaging process, after RF excitation, firstly completing layer selection through Z-direction gradient, namely selecting one layer to be imaged; then, turning on a magnetic field in the Y direction, so that precession speeds of magnetic moments at different Y positions are different, and turning off a Y gradient, so that the magnetic moment speeds at all the positions are restored to be the same, but phase shifts of different Y positions are different due to the difference of the precession speeds, and the process is called phase encoding; next, the gradient in the X direction is switched on, and the magnetic moments at different X positions differ in speed, a process called frequency encoding. So far, through phase coding and frequency coding, each position of a 2D image can be determined, signals acquired by a receiving coil are k-space signals, and the image can be obtained through Fourier transformation; and completing a new round of layer selection through the gradient in the Z direction, and repeating the process to obtain the 3D MRI image.
In MRI, the hydrogen protons in fat tissue and the hydrogen protons in other tissues in the human body are in different molecular environments, so that the resonance frequencies of the hydrogen protons and the hydrogen protons are different; when the hydrogen protons in fat and other tissues are excited by the radio frequency pulse at the same time, their relaxation times are also different. Signals are acquired at different echo times, and adipose tissue and non-adipose tissue exhibit different signal intensities. Using the above properties of different tissues in the human body, various pulse sequences for suppressing fat signals have been developed.
The Fat Saturation (fatat) method is a radio frequency selective Fat suppression technique. The basic principle is that the fat is selectively saturated by utilizing the slight difference of the resonance frequency of the fat and the water and adjusting the frequency and the bandwidth of the excitation pulse, and the fat protons do not generate signals, thereby obtaining the image only containing the water proton signals. At the beginning of the fatat sequence, a selected slice is first excited with a 90 ° radio frequency pulse (saturation pulse) having the same resonance frequency as fat to flip the macroscopic magnetization vector of the fat to the transverse (XOY) plane, a spoiling (phase-destroying) gradient pulse is applied immediately after the excitation pulse to destroy the phase consistency of the fat signal, and an imaging pulse is applied immediately thereafter. Because the time between the acquisition of the echo signal and the saturation pulse is very short (<100ms), the fat proton has insufficient time to recover the longitudinal magnetization vector, no signal is generated, and the purpose of fat inhibition is achieved.
In magnetic resonance imaging, chemical shift is a very important phenomenon because: when the static magnetic field intensity is not uniform, the precession frequencies of fat and water are biased by the influence of the local magnetic field. Magnetic field inhomogeneity can occur in regions where significant changes in anatomical morphology occur. FIG. 1 is a graph showing chemical shifts between water and fat, and as shown in FIG. 1, when the static magnetic field intensity is 1.5T, the chemical shift between water (W) and fat (F) is 220 Hz; when the static magnetic field intensity was 3T, the chemical shift between water and fat was 440 Hz.
The chemical shift phenomenon is more severe in high field systems (e.g., 3T systems). To avoid the negative effects of regional saturation bands and to avoid possible false activations of regions of interest, the current solution of 3T systems is to use a hard-coded approach to implicitly reduce the saturation band width. The method specifically comprises the following steps: the width of the saturation band is implicitly reduced to 85% of the actual user demand, this method assumes: within the 15% reduction region, the saturation pulse does not affect the region of interest when the worst case chemical shift occurs.
FIG. 2 shows a comparison of the chemical shifts of the saturation band without and with the hard-coding method. Wherein S represents a region to be suppressed such as: fat, I represents the region of interest. The dashed box B1 in the graph a is the saturation band actually set by the user, and the graph B is a diagram illustrating the worst-case chemical shift occurring when the saturation band shown in the graph a is adopted, so that when the worst-case chemical shift occurs, the chemical shift of the saturation band B1 may cause erroneous excitation of the region of interest I; the dashed box B2 in graph c, i.e. B1 with a 15% reduction in width, and the graph d is a schematic representation of the worst-case chemical shift that occurs with the saturation band shown in graph c, it can be seen that the chemical shift of the saturation band B2 does not result in a false excitation of the region of interest I when the worst-case chemical shift occurs.
Although the method of implicitly reducing the width of the saturation band can avoid the false excitation of the region of interest, the reduction of the saturation band reduces the saturation region, so that the suppression region is narrower than required, and the expected suppression effect is not achieved.
Disclosure of Invention
In view of this, the embodiments of the present invention provide a saturation band mri scanning method and apparatus on the one hand, and a magnetic resonance imaging system on the other hand, so as to avoid false excitation of a region of interest by a saturation pulse without changing the width of a saturation band.
The technical scheme of the embodiment of the invention is realized as follows:
a saturation band magnetic resonance imaging scan method, comprising:
acquiring the position of a saturation band of saturation band magnetic resonance imaging;
acquiring the position of an imaged region of interest;
taking a direction pointing from the saturation zone to the region of interest as a first direction;
determining the gradient direction of the selected layer;
and when the gradient direction of the selected layer is opposite to the first direction, the gradient sign of the applied selected layer gradient is negative and the corresponding magnetic field strength is gradually reduced.
The acquiring the position of the saturation band magnetic resonance imaging comprises: determining a center point of a saturation band of the saturation band magnetic resonance imaging;
the acquiring the location of the imaged region of interest includes: determining a center point of an imaging field of view (FOV);
the direction pointing from the saturation band to the region of interest as the first direction includes: a direction pointing from the center point of the saturation band to the center point of the FOV is taken as the first direction.
The method further comprises the following steps of applying a selective layer gradient on the saturation band according to the selective layer gradient direction:
and applying radio frequency saturation pulse on the selected layer of the layer selection gradient.
A saturated band magnetic resonance imaging scanner comprising:
the direction determining module is used for acquiring the position of a saturation band of saturation band magnetic resonance imaging, acquiring the position of an imaged region of interest, and taking the direction pointing to the region of interest from the saturation band as a first direction; determining the gradient direction of the selected layer;
and the layer selection gradient application control module is used for applying a layer selection gradient on the saturation band according to the layer selection gradient direction when the magnetic resonance imaging scanning of the saturation band starts, wherein the gradient sign of the applied layer selection gradient is positive and the corresponding magnetic field intensity is gradually increased when the gradient direction of the selected layer is the same as the first direction, and the gradient sign of the applied layer selection gradient is negative and the corresponding magnetic field intensity is gradually decreased when the gradient direction of the selected layer is opposite to the first direction.
The direction determination module determining a location of a saturation band magnetic resonance imaging comprises: determining a center point of a saturation band of the saturation band magnetic resonance imaging;
the orientation determination module determining the location of the imaged region of interest comprises: determining a center point of an imaging field of view (FOV);
the direction determination module takes a direction pointing from the saturation zone to the region of interest as a first direction including: a direction pointing from the center point of the saturation band to the center point of the FOV is taken as the first direction.
The apparatus further comprises: and the radio frequency saturation pulse application control module is used for applying the radio frequency saturation pulse on the selected layer of the selected layer gradient.
A saturated band magnetic resonance imaging scanner comprising: a memory and a processor accessible to the memory, the memory storing instructions that, when executed by the processor, cause the processor to perform the steps of the method as described in any one of the above.
A magnetic resonance imaging system comprising a saturated band magnetic resonance imaging scanner as claimed in any one of the preceding claims.
In the embodiment of the invention, when the gradient direction of the selected layer is the same as the direction of the saturated zone pointing to the region of interest, the gradient sign of the applied selected layer gradient is positive and the corresponding magnetic field intensity is gradually increased, otherwise, the gradient sign of the applied selected layer gradient is negative and the corresponding magnetic field intensity is gradually decreased, so that the chemical shift direction caused by the selected layer gradient in the saturated zone is always far away from the region of interest, and the false excitation of the region of interest by the saturated pulse is avoided on the premise of not changing the width of the saturated zone.
Drawings
The foregoing and other features and advantages of the invention will become more apparent to those skilled in the art to which the invention relates upon consideration of the following detailed description of a preferred embodiment of the invention with reference to the accompanying drawings, in which:
FIG. 1 is a schematic representation of the chemical shift between water and fat;
FIG. 2 is a graph comparing chemical shifts of saturation bands without and with a hard-coding method;
FIG. 3 is a flowchart of a saturated band MRI scanning method according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of the relationship between the chemical shift direction of the suppression region and the sign of the gradient and the magnetic field strength provided by an embodiment of the present invention;
FIG. 5 is a schematic illustration of a slice selection gradient setup using the present invention;
FIG. 6 is a comparison graph of a simulation experiment for a saturation band MRI using the prior art hard coding method and using the present invention when the saturation band exists only on one side of the center of the FOV;
FIG. 7 is a comparison graph of a simulation experiment for performing magnetic resonance imaging in the saturation zone using the prior hard-coding method and the present invention when the saturation zones are present at both sides of the center of the FOV, respectively;
FIG. 8 is a comparison graph of imaging results of in vivo experiments performed on a magnetic resonance spectroscopy system using the existing hard-coded method and the present invention, respectively;
fig. 9 is a schematic structural diagram of a saturated band mri scanner according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of a saturated band mri scanner according to another embodiment of the present invention.
Wherein the reference numbers are as follows:
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail by referring to the following examples.
Fig. 3 is a flowchart of a saturation band mri scanning method according to an embodiment of the present invention, which includes the following specific steps:
step 301: acquiring the position of a saturation band of saturation band magnetic resonance imaging, acquiring the position of an imaged region of interest, and taking the direction pointing from the saturation band to the region of interest as a first direction.
Step 302: and determining the gradient direction of the selected layer.
The saturation zone is perpendicular to the region of interest, and the selection layer gradient is perpendicular to the saturation zone, so that the selection layer gradient direction has two kinds: one in the same direction as pointing from the saturation band to the region of interest and the other in the opposite direction from pointing from the saturation band to the region of interest.
Step 303: and when the gradient direction of the selected layer is opposite to the first direction, the gradient sign of the applied selected layer gradient is negative and the corresponding magnetic field strength is gradually reduced.
And applying a radio frequency saturation pulse on the selected layer while selecting the excitation layer through the layer selection gradient.
In the above embodiment, when the direction of the slice selection gradient is the same as the direction in which the saturation band points to the region of interest, the applied slice selection gradient has a positive gradient sign and gradually increases the corresponding magnetic field strength, otherwise, the applied slice selection gradient has a negative gradient sign and gradually decreases the corresponding magnetic field strength, so that the chemical shift direction caused by the slice selection gradient in the saturation band is always far away from the region of interest, and therefore, the false excitation of the region of interest by the saturation pulse is avoided on the premise of not changing the width of the saturation band.
In an alternative embodiment, the step 301 of acquiring the position of the saturation band magnetic resonance imaging includes: determining a center point of a saturation band of the saturation band magnetic resonance imaging;
acquiring the location of the imaged region of interest includes: determining a center point of a FOV (Field of View);
regarding a direction pointing from the saturation band to the region of interest as a first direction includes: a direction pointing from the center point of the saturation band to the center point of the FOV is taken as the first direction.
By the above embodiments it is ensured that the direction of the chemical shift induced by the gradient of the selective layer in the saturation zone is always far away from the region of interest.
Fig. 4 is a schematic diagram of the relationship between the chemical shift direction of the suppression region and the sign of the gradient and the magnetic field strength provided by the embodiment of the present invention. S1, S2 in the figure represent the region to be suppressed, and I is the region of interest. Panel a shows the case where no gradient is applied, and where there is no chemical shift across I at S1 and S2; the graph b is the case of applying gradually a gradient with gradually increasing magnetic field strength from negative to positive sign from left to right, and it can be seen that the chemical shift direction of the left S1 is to the left, i.e. away from I, and the chemical shift direction of the right S2 is also to the left, i.e. close to I, as shown by the black arrows in the graph b; the graph c is a case where a gradient with a sign gradually increasing from negative to positive and a magnetic field strength gradually increasing is applied from right to left, and it can be seen that the chemical shift direction of the left S1 is rightward, i.e., closer to I, and the chemical shift direction of the right S2 is also rightward, i.e., farther from I, as indicated by black arrows in the graph c.
As can be seen from fig. 4 b, c, when the applied magnetic field strength over the region to be suppressed is lower than the applied magnetic field strength over the region of interest, the chemical shift direction of the region to be suppressed will be away from the region of interest.
So that in order to shift the chemical shift of the saturation band away from the region of interest, the correspondence shown in table 1 can be obtained:
TABLE 1
FIG. 5 is a schematic representation of a slice selection gradient setup using the present invention. Where S denotes a region to be suppressed, and I1 and I2 denote regions of interest. Fig. a1, b1 are schematic diagrams of using a correct slice selection gradient, and fig. a2, b2 are schematic diagrams of using an incorrect slice selection gradient, specifically:
in the diagram a1, the saturation band B1 is to the left of the regions of interest I1, I2, the slice selection gradient direction is from left to right, and the sign of the slice selection gradient and the magnetic field strength are: from negative to positive, increasing gradually, i.e. in case 3 in table 1, it can be seen that the chemical shift direction of the saturation band B1 is to the left, i.e. away from the regions of interest I1, I2;
in fig. a2, the position of the saturation band B1 and the direction of the slice selection gradient are the same as in fig. a1, but the sign of the slice selection gradient and the magnetic field strength become: from positive to negative, decreasing progressively, it can be seen that the chemical shift direction of the saturation band B1 is to the right, i.e. close to the regions of interest I1, I2;
in the diagram B1, the saturation band B2 is to the right of the regions of interest I1, I2, the slice selection gradient direction is from right to left, the sign of the slice selection gradient and the magnetic field strength are: from negative to positive, increasing gradually, i.e. in case 2 in table 1, it can be seen that the chemical shift direction of the saturation band B2 is to the right, i.e. away from the regions of interest I1, I2;
in fig. B2, the position of the saturation band B2 and the direction of the slice selection gradient are the same as in fig. B1, but the sign of the slice selection gradient and the magnetic field strength become: from positive to negative, decreasing gradually, it can be seen that the chemical shift direction of the saturation band B2 is to the left, i.e. close to the regions of interest I1, I2.
The following are provided as proof of the simulation experiments of the present invention:
fig. 6 is a comparison graph of simulation experiments for performing saturation band mri using the conventional hard-coding method and the present invention when a saturation band exists only on the center side of the FOV. In the figure, the upper small cylinder is filled with oil, and the lower large cylinder is filled with GuSO4 (copper sulfate). Wherein the rectangular grids in the upper panels a1, a2, a3 represent saturation bands, and the white arrows in the lower panels a1, a2, a3 represent chemical shift directions;
the upper and lower two graphs a1 are chemical shift graphs of a saturation band when the saturation band is implicitly reduced by the existing hard coding method and a magnetic resonance imaging scan is performed by TSE (turbo inpin echo), wherein the width of the saturation band is implicitly reduced by 15%. It is clear that the chemical shift direction of the saturation band is to the right, i.e. close to the center of the FOV, and that a reduction of the saturation band avoids a wrong excitation of the right tissue.
The upper and lower two graphs a2 are chemical shift graphs of saturation band when setting the slice selection gradient by the method provided by the invention and using TSE to carry out magnetic resonance imaging scanning, wherein, by setting the sign and magnetic field intensity of the slice selection gradient, the chemical shift of the saturation band is left, namely far away from the right tissue, and the width of the saturation band does not need to be changed.
The upper and lower two graphs a3 are chemical shift graphs of the saturation band in a magnetic resonance imaging scan using a slice selection gradient with sign and field strength change opposite to those of graph a2 and using a TSE, wherein the sign and field strength change of the slice selection gradient are opposite to those of graph a2, so that the chemical shift of the saturation band is rightward, i.e. close to the right tissue, and it can be seen that the chemical shift of the saturation band is rightward, which results in false excitation of the right tissue by the TSE.
As can be seen from fig. 6, the chemical shift direction of the saturation band can be changed by changing the sign of the slice selection gradient and the magnetic field strength.
It should be noted that, in the partial area of fig. 6, there are small white characters, which are attached to the original picture, and if the small white characters are removed, the imaging details are deleted at the same time, so that the small white characters are not removed here, the small white characters are not directly related to the scheme of the present invention, and the unclear small white characters do not affect the explanation of the present invention.
Fig. 6 shows a case where a saturation band exists only on the center side of the FOV. Fig. 7 shows the case where saturation zones are present on both sides of the center of the FOV. The white arrows in figures a, b, c indicate the direction of increasing gradient magnetic field strength, wherein:
fig. a shows that the saturation band is set by the existing hard coding method, i.e. the wide band of the saturation band is reduced by 15% compared to the width set by the user;
the saturation band shown in the graph a is adopted in the graph b, and it can be seen that the gradient magnetic field intensity increases in the same direction on the left and right saturation bands from right to left, and the chemical shift directions of the left and right saturation bands are right at the moment, namely, the saturation band on one side is close to the center of the FOV, and the saturation band on the other side is far away from the center of the FOV;
the width of the saturation band is not changed by the method, the increasing directions of the gradient magnetic field intensity on the left saturation band and the right saturation band are opposite, the gradient magnetic field intensity on the left saturation band increases from left to right, the gradient magnetic field intensity on the right saturation band increases from right to left, the chemical shift direction of the left saturation band is left, the chemical shift direction of the right saturation band is right, and the chemical shift directions of the two saturation bands are far away from the center of the FOV;
plot d also used the method of the present invention, but the gradient field increased in the opposite direction to plot c on the right two saturation bands, and it can be seen that the chemical shift direction of both saturation bands is close to the center of the FOV.
Therefore, when saturation bands exist on both sides of the FOV, the chemical shift directions of the saturation bands on both sides are consistent when the existing hard coding method is adopted, and the invention can respectively apply layer selection gradients with different symbols and magnetic field strengths on the saturation bands on both sides, so that the chemical shift directions of the two saturation bands are different, and the false excitation of the saturation pulses to the interested region can be completely avoided.
It should be noted that, in the partial area of fig. 7, there are small white characters, which are attached to the original picture, and if the small white characters are removed, the imaging details are deleted at the same time, so that the small white characters are not removed here, the small white characters are not directly related to the scheme of the present invention, and the unclear small white characters do not affect the explanation of the present invention.
FIG. 8 is a contrast diagram of the imaging results of in vivo experiments performed on a magnetic resonance spectroscopy system using the prior art hard-coding method and the present invention, respectively. Wherein, c-spine of the volunteer is imaged, and imaging parameters are as follows: FOV size 220 × 220mm (mm), layer thickness 3mm, TE/TR (echo time/repetition time) 108/3500ms (millisecond), phase OS (oversampling rate) 80%, BaseRes (base resolution) 384, PhaseRes (ratio of phase resolution to base resolution) 70%, voxel size 0.6 × 3mm, BW (bandwidth)/pixel 260HZ (hertz), ESP (echo interval) 10.8ms, and ETL (echo chain length) 19.
Fig. 8 a1 and b1 are graphs of imaging results using a conventional hard coding method, and a2 and b2 are graphs of imaging results using the present invention. The images above a1, a2, b1 and b2 are schematic diagrams of positions of saturated zones corresponding to a1, a2, b1 and b 2. Obviously, since the saturation bands of the a2 and the b2 are not reduced and the region of interest is not excited by mistake, the saturation regions are more accurate and the imaging result is clearer.
It should be noted that, in the partial area of fig. 8, there are small white characters, which are attached to the original picture, and if the small white characters are removed, the imaging details are deleted at the same time, so that the small white characters are not removed here, the small white characters are not directly related to the scheme of the present invention, and the unclear small white characters do not affect the explanation of the present invention.
Fig. 9 is a schematic structural diagram of a saturated band mri scanner 90 according to an embodiment of the present invention, which mainly includes:
the direction determining module 91 is configured to acquire a position of a saturation zone of the saturation zone magnetic resonance imaging, acquire a position of an imaged region of interest, and use a direction pointing from the saturation zone to the region of interest as a first direction; and determining the gradient direction of the selected layer.
And the selective layer gradient application control module 92 is configured to apply a selective layer gradient on the saturation band according to the selective layer gradient direction when the saturation band magnetic resonance imaging scanning starts, wherein the gradient sign of the applied selective layer gradient is positive and the corresponding magnetic field strength gradually increases when the selective layer gradient direction is the same as the first direction, and the gradient sign of the applied selective layer gradient is negative and the corresponding magnetic field strength gradually decreases when the selective layer gradient direction is opposite to the first direction.
In an alternative embodiment, the determining the position of the saturation band magnetic resonance imaging by the direction determining module 91 comprises: determining a center point of a saturation band of the saturation band magnetic resonance imaging;
the direction determination module 91 determines the location of the imaged region of interest including: determining a center point of an imaging field of view (FOV);
the direction determining module 91 takes a direction pointing from the saturation zone to the region of interest as a first direction including: a direction pointing from the center point of the saturation band to the center point of the FOV is taken as the first direction.
In an optional embodiment, the apparatus further comprises: and the radio frequency saturation pulse application control module is used for applying the radio frequency saturation pulse on the selected layer of the selected layer gradient.
Fig. 10 is a schematic structural diagram of a saturated band mri scanner 100 according to another embodiment of the present invention, which mainly includes: a memory 101 and a processor 102 having access to the memory 101, the memory 101 storing instructions that, when executed by the processor 102, cause the processor 102 to perform the steps of the saturated band magnetic resonance imaging scan method as described in steps 301-303.
An embodiment of the present invention further provides a magnetic resonance imaging system, including the saturated band magnetic resonance imaging scanning apparatus as described in any one of the above.
It should be noted that, because the sign of the slice selection gradient and the magnetic field strength are determined by comparing the direction of the slice selection gradient with the direction pointing from the saturation zone to the region of interest or vice versa, the invention does not need to consider whether the saturation zone is symmetrical, i.e., the invention is applicable to both symmetrical and asymmetrical saturation zones.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (8)
1. A method of saturated band magnetic resonance imaging scanning, comprising:
acquiring the position of a saturation band of saturation band magnetic resonance imaging;
acquiring the position of an imaged region of interest;
taking a direction pointing from the saturation zone to the region of interest as a first direction;
determining the gradient direction of the selected layer;
and when the gradient direction of the selected layer is opposite to the first direction, the gradient sign of the applied selected layer gradient is negative and the corresponding magnetic field strength is gradually reduced.
2. The method of claim 1, wherein the acquiring the location of the saturation band magnetic resonance imaging comprises: determining a center point of a saturation band of the saturation band magnetic resonance imaging;
the acquiring the location of the imaged region of interest includes: determining a center point of an imaging field of view (FOV);
the direction pointing from the saturation band to the region of interest as the first direction includes: a direction pointing from the center point of the saturation band to the center point of the FOV is taken as the first direction.
3. The method of claim 1, wherein applying the slice selection gradient in the slice selection gradient direction over the saturation band further comprises:
and applying radio frequency saturation pulse on the selected layer of the layer selection gradient.
4. A saturated band magnetic resonance imaging scanner (90), comprising:
a direction determination module (91) for acquiring the position of a saturation band of the saturation band magnetic resonance imaging, acquiring the position of an imaged region of interest, and regarding a direction pointing from the saturation band to the region of interest as a first direction; determining the gradient direction of the selected layer;
and the selective layer gradient application control module (92) is used for applying a selective layer gradient on the saturation band according to the selective layer gradient direction when the saturation band magnetic resonance imaging scanning starts, wherein the gradient sign of the applied selective layer gradient is positive and the corresponding magnetic field intensity is gradually increased when the selective layer gradient direction is the same as the first direction, and the gradient sign of the applied selective layer gradient is negative and the corresponding magnetic field intensity is gradually decreased when the selective layer gradient direction is opposite to the first direction.
5. The apparatus (90) of claim 4, wherein the direction determination module (91) determines the location of the saturation band magnetic resonance imaging comprises: determining a center point of a saturation band of the saturation band magnetic resonance imaging;
the direction determination module (91) determining the location of the imaged region of interest comprises: determining a center point of an imaging field of view (FOV);
the direction determination module (91) regarding a direction pointing from a saturation zone to a region of interest as a first direction comprises: a direction pointing from the center point of the saturation band to the center point of the FOV is taken as the first direction.
6. The apparatus (90) of claim 4, wherein the apparatus (90) further comprises: and the radio frequency saturation pulse application control module is used for applying the radio frequency saturation pulse on the selected layer of the selected layer gradient.
7. A saturated band magnetic resonance imaging scanner (100), comprising: a memory (101) and a processor (102) having access to the memory (101), the memory (101) storing instructions which, when executed by the processor (102), cause the processor (102) to perform the steps of the method according to any one of claims 1 to 3.
8. A magnetic resonance imaging system comprising a saturated band magnetic resonance imaging scanner (90, 100) according to any one of claims 4 to 7.
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| WO2024087249A1 (en) * | 2022-10-25 | 2024-05-02 | 无锡鸣石峻致医疗科技有限公司 | Signal saturation method for achieving spatial selection under non-uniform field, and medium |
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